The act of copying, mimicing, a 'funny' or humerous, action by a friend. Going over the top, with this action, either causing damage, or getting the whole group in trouble.
This is a bad social action. In order to pull a correct Howard, you have to deny the Howard itself. Thus blame someone else for the trouble, and/or damage caused
Basically; a fuck up.

After Ted, started to throw his pen, at a friend, for a joke. Bob, Pulling a Howard, by through his ruler at the teacher. Then denied ever doing so, even though he was seen doing it. Everybody got in trouble.